Technical Abstract:
Introducing atrazine (ATR) degraders into riparian vegetative buffer strips (VBS) can be a promising bioremediation approach to accelerate the degradation of ATR and its degradation products deposited into VBS by surface runoff. A growth chamber study was conducted to investigated the synergistic effect of introducing the ATR degrader Pseudomonas sp. ADP into switchgrass (Panicum virgatum) rhizospheres on ATR degradation. The results suggested that the introduction of the Pseudomonas sp. ADP rapidly enhanced the rates of ATR degradation. More than 99 percent of applied 14C-ATR was degraded within first 72 hours of inoculation and 54.5 percent of applied 14C-ATR was mineralized to CO2. Hydroxylated metabolites, including hydroxyatrazine and desethylhydroxyatrazine, were the major degradation products in the inoculated treatments, while N-dealkylated metabolites (desethylatrazine) were the major degradation products in the un-inoculated treatments. Switchgrass rhizospheres sustained the copy number of atzA at higher levels than the control (bulk soil). In the presence of switchgrass, atzA copy number was stimulated for the first two weeks, but steadily decreased until leveling out from days 24-37. The lack of complete mineralization may be attributed to the loss of atzA gene copy number over time which signified a loss of ATR-degrading potential in the rhizosphere. The addition of ATR-degrading bacteria into switchgrass VBS has the potential to sustain enhanced degradation that can effectively remove entrapped ATR, preventing contamination of surface and ground waters.